Is CVE-2026-122127 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-122127 being exploited in the wild.

How severe is CVE-2026-122127?

High severity, with a CVSS score of 7.5, published 4 November 2026.

Which products and versions are affected?

CESNET Ipfixcol2 2.7.1 before 2.9.0.

Is there a fix for CVE-2026-122127?

Yes: fixed in ipfixcol2 2.9.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-122127 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-122127?

Check whether you run CESNET Ipfixcol2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-122127: CESNET ipfixcol2 heap buffer overflow in LZ4 decompression

CVE-2026-122127 · Severity: high · CVSS 7.5 · Published 2026-11-04

CESNET ipfixcol2 is a high-performance NetFlow and IPFIX flow data collector used to receive and process network traffic data. A heap buffer overflow vulnerability in the LZ4 decompression component allows unauthenticated remote attackers to write controlled data past buffer boundaries and crash the collector, potentially leading to denial of service or code execution.

Technologies: CESNET Ipfixcol2. Vendors: CESNET.

Quick answers

Is CVE-2026-122127 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-122127 being exploited in the wild.
How severe is CVE-2026-122127?: High severity, with a CVSS score of 7.5, published 4 November 2026.
Which products and versions are affected?: CESNET Ipfixcol2 2.7.1 before 2.9.0.
Is there a fix for CVE-2026-122127?: Yes: fixed in ipfixcol2 2.9.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-122127 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-122127?: Check whether you run CESNET Ipfixcol2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: ipfixcol2 2.9.0

Technical details

The vulnerability exists in Lz4Decoder.cpp where decompressed buffer size validation is insufficient. An attacker can send a crafted IPFIX message with a small ring buffer_size in the start header followed by a large decompressed_size in the compression header, causing LZ4_decompress_safe_continue to write up to 65535 bytes beyond allocated buffer boundaries. The vulnerability is triggered by network peers without authentication via TCP input plugin.

Affected products

CESNET ipfixcol2 2.7.1 before 2.9.0

Timeline

2026-11-04: disclosed

References

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